Connecting structure for vacuum pump

ABSTRACT

Provided is a connecting structure for a vacuum pump, which can block propagation of electrical noise, generated by a main body of the vacuum pump. Between both ends of a connection piping for connecting the vacuum pump to a vacuum chamber of an apparatus to be connected with and evacuated by the vacuum pump, there is interposedly provided an electrical insulating portion formed of an insulating material so as to provide electrical insulation therebetween. The electrical insulation portion may be provided to a connection piping member such as a damper (or a valve depending on the connection arrangement) for absorbing mechanical vibrations.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a connecting structure forconnecting a vacuum pump. In particular, it relates to a connectingstructure for a vacuum pump, which is capable of blocking propagation ofelectrical noise generated by a main body of the vacuum pump.

[0003] 2. Description of the Related Art

[0004] A conventional connecting structure used for connecting a vacuumpump (hereinafter referred to as the “connecting structure for a vacuumpump) is shown in FIG. 6.

[0005] Referring to FIG. 6, when a vacuum pump 101 is connected throughconnection piping to a measuring apparatus such as an electronmicroscope which requires a vibration-free environment to operate, adamper 105 as a vibration absorbing member is interposedly disposedwithin the connection piping. Electron microscope etc. are provided in avacuum chamber 103 being a measurement chamber. The vacuum pump 101 issuspended from the vacuum chamber 103 with the damper 105 so as to beconnected thereto.

[0006] The damper 105 is constructed so that a bellows 105 a issandwiched between flanges 107 and 109 arranged on its both ends. Thebellows 105 a absorbs vibrations between a suction port of the vacuumpump 101 and the vacuum chamber 103.

[0007] The bellows 105 a is formed of a stainless material in order tohave a mechanical strength sufficient to protect itself in an event ofthe vacuum pump 101 being broken due to centrifugal force.

[0008] Connection between the damper 105 and the vacuum chamber 103 isprovided by means of the flange 109 formed at the upper end of thedamper 105 and a flange 113 of the vacuum chamber 103. Connectionbetween the damper 105 and the vacuum pump 101 is provided by means ofthe flange 107 formed at the lower end of the damper 105 and a suctionflange 111 of the vacuum pump 101.

[0009] In the thus constructed connecting structure for the vacuum pump101, operating the vacuum pump 101 for suction and decompressionpurposes allows decompression of the vacuum chamber 103 to be effectedfrom the suction port of the vacuum pump 101 through the connectionpiping. At this time, vibrations are generated by a main body of thevacuum pump 101 due to such factors as an unbalanced state of a rotorand cogging torque acting during a rotational drive. Such mechanicalvibrations of the vacuum pump 101 are blocked out by the damper 105,whereby the vibrations do not reach the vacuum chamber 103 so that avibration-free environment can be maintained.

[0010] However, in the above construction, the damper 105 whichconstitutes the above-described connection piping is formed of amaterial with high electrical conductivity such as a stainless material,including its portions of the both flanges 107 and 109. This may lead toa troublesome situation where electrical noise generated by electricequipment such as a motor disposed within the vacuum pump 101 propagatesinto an apparatus to be connected with the vacuum pump 101. Inparticular, in a case of a measuring apparatus, which requires for itsoperation an environment isolated of disturbances such as mechanicalvibrations and electrical noise, even if it is effectively guardedagainst intrusion of disturbances from the outside, disturbancesgenerated by an associated apparatus such as the vacuum pump 101connected to the measuring apparatus may induce reduction in themeasurement accuracy thereof.

SUMMARY OF THE INVENTION

[0011] The present invention has been devised in view of theabove-described drawbacks of the conventional art. Therefore, an objectof the present invention is to provide a connecting structure for avacuum pump, which is capable of blocking propagation of electricalnoise generated by a main body of the vacuum pump.

[0012] In order to attain the above object, according to the presentinvention, there is provided a connecting structure for a vacuum pumpcomprising: a vacuum pump; an apparatus to be evacuated by the vacuumpump; connection means for connecting the apparatus to be evacuated withthe vacuum pump; and an electrical insulating portion which isinterposedly provided within the connection means and formed of anelectrical insulating material to provide electrical insulation.

[0013] The electrical insulating portion disposed interposedly within aconnection piping serves to block out propagation of electrical noisegenerated by the vacuum pump. Therefore, an electrical insulatingenvironment that is free from electrical influences exerted by thevacuum pump can be ensured even when the vacuum pump is connected to ameasuring apparatus that is highly susceptible to the influence ofelectromagnetic waves.

[0014] Further, the present invention is also characterized in that theelectrical insulating portion is formed using at least one materialselected from resin, rubber, and ceramic.

[0015] Further, the present invention is characterized in that aprotective cover corresponding to the vacuum pump is provided, aroundthe outer periphery of the connection means.

[0016] Since the protective cover provides effective protection in anevent of breakage of the vacuum pump, a greater degree of freedom isafforded in designing the electrical insulating portion.

[0017] Further, the present invention is characterized in that theelectrical insulating portion is arranged in a connecting piping membersuch as a damper for absorbing mechanical vibrations and a valve foradjusting suction flow rate.

[0018] Since the electrical insulating portion is provided to theconnecting piping member such as the damper and the valve, electricalinsulating properties can be ensured by connecting the damper or thevalve through piping, without the necessity of attaching a memberdedicated for providing electrical insulation.

BRIEF DESCRIPTION OF THE DRAWING

[0019] In the accompanying drawings:

[0020]FIG. 1 is a side elevation view of a connecting structure for avacuum pump in accordance with a first embodiment of the presentinvention;

[0021]FIG. 2 is a view showing a vertical cross section of a turbomolecular pump;

[0022]FIG. 3 is a view showing an example in which a part of a bellowsis circumferentially formed from an electrical insulating material;

[0023]FIG. 4 is a view showing an example in which an electricalinsulating portion made up of an insulating coating, an insulatingplate, or the like is interposedly provided on a flange surface;

[0024]FIG. 5 is a side elevation view of a connecting structure for avacuum pump in accordance with a second embodiment of the presentinvention; and

[0025]FIG. 6 is a view showing a conventional connecting structure for avacuum pump.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Embodiments of the present invention will be describedhereinbelow. FIG. 1 is a side elevation view of a connecting structurefor a vacuum pump in accordance with a first embodiment of the presentinvention. Note that like reference numerals are given to denoteportions that are identical to those of FIG. 6, and an explanationthereof is omitted here.

[0027] Referring to FIG. 1, a vacuum pump 101 such as a turbo molecularpump is connected through piping to a vacuum chamber 103 in a hangingfashion, with a damper 1 for absorbing mechanical vibrations andproviding electrical insulation being interposedly disposed between asuction port thereof and the vacuum chamber 103 being a measurementchamber.

[0028] The damper 1 has flanges 3 and 5 arranged on its both ends, and abellows 7 capable of absorbing mechanical vibrations is provided betweenthe flanges 3 and 5. In addition to being configured to absorbmechanical vibrations, the bellows 7 is formed as an electricalinsulating portion made up of an electrical insulating material such asresin, rubber, and ceramic. A protective cover 9 may be provided aroundthe outer periphery of the bellows 7 if necessary.

[0029] The protective cover 9 is formed integrally with one of the bothflanges of the damper 1, for example with the lower flange 3 (or theupper flange 5) as depicted in the figure, in such a way as to surroundthe bellows 7. The protective cover 9 is made from metallic materialetc. that have a mechanical strength sufficient to provide protectionagainst scattered fragments of the vacuum pump 101 should it be brokendue to centrifugal force. Note that the protective cover 9 may not beprovided if the bellows 7 itself has a sufficient mechanical strength.

[0030] The vacuum pump 101 is for example a decompression and suctionpump such as a turbo molecular pump.

[0031]FIG. 2 shows a vertical cross section of a turbo molecular pump121.

[0032] Referring to FIG. 2, a suction flange 111 is formed at the upperend of the turbo molecular pump 121. Provided further inward therefromis a rotor 123 having multiple stages of a plurality of rotor blades 122a, 122 b, 122 c and so on, each being formed of a turbine blade forsucking and discharging gas.

[0033] Upper radial electromagnets 124 consist of four electromagnetsarranged in pairs with respect to x and y axes. Four inductance-typeupper radial sensors 127 are provided proximate to and in associationwith these upper radial electromagnets 124. Each upper radial sensor 127is configured to detect a radial displacement of the rotor 123 and sendsit to a magnetic bearing controlling unit in a not-shown pump controlapparatus.

[0034] On the basis of a displacement signal detected by each upperradial sensor 127, the magnetic bearing controlling unit controlsmagnetic excitation of the upper radial electromagnets 124 through acompensation circuit having a PID control function, thereby regulating aradial position of an upper portion of the rotor 123. Such positionalregulation is performed in x-axis as well as y-axis directions.

[0035] Likewise, lower radial electromagnets 125 and lower radialsensors 128 are provided in a manner similar to that of the upper radialelectromagnets 124 and the upper radial sensors 127 described above,thus regulating a radial position of a lower portion of the rotor 123.

[0036] Further, axial electromagnets 126 are arranged so as to opposeeach other through a metallic disk 131 provided to the rotor 123. Also,there is provided an axial sensor 129 for detecting an axialdisplacement of the rotor 123, which is configured to send an axialdisplacement signal to the magnetic bearing controlling unit.

[0037] Magnetic excitation of each axial electromagnet 126 is controlledby the magnetic bearing controlling unit on the basis of the thusobtained axial displacement signal, whereby the rotor 123 ismagnetically levitated in its axial direction.

[0038] A motor 141 has a plurality of magnetic poles circumferentiallyarranged so as to encircle the rotor 123. Each magnetic pole iscontrolled by a motor control unit of the pump control apparatus so asto rotationally drive the rotor 123 through an electromagnetic forceacting between the each magnetic pole and the rotor 123.

[0039] Next, description will be made of operation of a connectingstructure for the vacuum pump 101 in accordance with an embodiment ofthe present invention.

[0040] When the vacuum pump 101 is activated, the vacuum chamber 103being a measurement chamber is decompressed to vacuum through theconnection piping that includes the damper 1. Mechanical vibrations andelectrical noise, which the vacuum pump 101 generates at this time, aretransmitted to the damper 1 that is connected to the suction flange 111.

[0041] At the damper 1, the mechanical vibrations generated by thevacuum pump 101 are received by the bellows 7, whereby the mechanicalvibrations are absorbed before reaching the vacuum chamber 103 being ameasurement chamber. The damper 1 also blocks out electrical noisegenerated by the vacuum pump 101 with the bellows 7 having electricalinsulating properties.

[0042] Therefore, with the connecting structure for the vacuum pump 101in accordance with the present invention, mechanical vibrations andelectrical noise generated by the vacuum pump 101 are effectivelyblocked out before propagating into an apparatus to which the vacuumpump is connected through piping.

[0043] As described above, the damper 1 is adapted primarily to absorbthe mechanical vibrations and provide electrical insulation between thesuction port of the vacuum pump 101 and the vacuum chamber 103 being ameasurement chamber. As such, it is sufficient for the above function tobe realized to constitute the electrical insulating portion thereof asbeing capable of providing electrical insulation between the bothflanges 3 and 5. Therefore, the above-described construction of thedamper 1 is by no means limitative and the damper 1 may be implementedin a variety of forms.

[0044] Specifically, as depicted in FIG. 3, a part 7 a of the bellows 7may be circumferentially formed from an electrical insulating material,or at least one of the both flanges 3 and 5 may be formed of anelectrical insulating material. Alternatively, as shown in FIG. 4, anelectrical insulating portion 5a consisting of an insulating coating, aninsulating plate, or the like may be provided on a surface of one of theboth flanges 3 and 5 and fastened thereto with an insulating bolt. Whenformed of a buffer material such as rubber, the electrical insulatingportion can also function to absorb mechanical vibrations, in additionto having electrical insulating properties.

[0045] To provide effective protection in an event of the vacuum pump101 being broken due to centrifugal force, a protective cover 9 may beprovided so as to surround the outer periphery of the bellows 7, thusallowing less stringent design conditions to be applied regarding themechanical strength of the bellows 7. This translates into a wider rangeof choice in the construction of the bellows 7, including use of avariety of materials such as resin, rubber, ceramic, or the like as itsmaterial, thus permitting a greater freedom of its design.

[0046] The method for attaching the protective cover 9 may take avariety of forms. The only requirement in this case is to constitute theprotective cover 9 so as to surround the outer periphery of the bellows7 so that it can receive fragments of the vacuum pump 101 which arescattered penetratingly through the bellows 7 when breakage occurs inthe vacuum pump 101. Therefore, attachment of the protective cover 9 maybe performed by fastening the protective cover 9 that is formedseparately from the damper 1, together with one of the both flanges 3and 5.

[0047] Next, description will be made of a second embodiment of thepresent invention.

[0048]FIG. 5 is a side elevation view of a connecting structure for thevacuum pump 101 in accordance with a second embodiment of the presentinvention. Note that like reference numerals are given to denoteportions that are identical to those of FIGS. 1 and 6, and anexplanation thereof are omitted here.

[0049] Referring to FIG. 5, a damper 105 and a valve 11 are arranged inseries through piping connection between a vacuum pump 101 and a vacuumchamber 103 being a measurement chamber. A flange 17 at the upper end ofthe valve 11 is coupled with a flange 113 of the vacuum chamber 103being a measurement chamber. Also, a flange 15 at the lower end of thevalve 11 is coupled with a flange 109 at the upper end of the damper105.

[0050] The valve 11 is a pressure control valve for controlling apressure within the vacuum chamber 103 on the measurement chamber side.The valve 11 is constructed such that it constitutes an electricalinsulating portion in its entirety, or the electrical insulating portionis interposedly formed between the both flanges 15 and 17.

[0051] In the case where the whole of the valve 11 is to be constructedas the electrical insulating portion, its main body casing is formedusing an electrical insulating material. As a structural example inwhich the electrical insulating portion is interposingly providedbetween the both flanges 15 and 17, at least one of the both flanges 15and 17 is formed of an electrical insulating material, as in the case ofconstructing the damper 1 described above.

[0052] Alternatively, an electrical insulating portion consisting of aninsulating coating, an insulating plate, or the like may be interposedlyprovided on a surface of one of the both flanges 15 and 17 and fastenedthereto with an insulating bolt. In this case, using a buffer materialsuch as rubber for the electrical insulating portion allows theelectrical insulating portion to have not only electrical insulatingproperty but also have a mechanical vibration absorbing function aswell. The present construction is similar to that for the aforementioneddamper 1 also in this respect.

[0053] In this way, the electrical insulating portion is interposedlyprovided within the connection piping between the vacuum pump 101 andthe vacuum chamber 103 being a measurement chamber. Therefore, themechanical vibrations generated by the vacuum pump 101 are absorbed bythe damper 105, while the associated electrical noise is blocked out bythe electrical insulating portion of the valve 11.

[0054] As has been described above, according to the present invention,the electrical insulating portion is interposedly provided within theconnection piping extending from the vacuum pump to an apparatus towhich the vacuum pump is connected. Therefore, propagation of theelectrical noise that is generated by the vacuum pump is effectivelyblocked by the electrical insulating portion.

[0055] Accordingly, even in the case where the vacuum pump is connectedto a measuring apparatus which requires for its operation anelectromagnetic insulating environment, an electrical insulatingenvironment is ensured, while eliminating an influence of electricalnoise or the like generated by the vacuum pump, in addition to ensuringa vibration-free environment by means of the damper.

What is claimed is:
 1. A connecting structure for a vacuum pump,comprising: a vacuum pump; an apparatus to be evacuated by the vacuumpump; connection means for connecting the apparatus to be evacuated withthe vacuum pump; and an electrical insulating portion which is providedwithin the connection means and formed of an electrical insulatingmaterial to provide electrical insulation.
 2. A connecting structure fora vacuum pump according to claim 1, wherein the electrical insulatingportion is formed of at least one material selected from the groupconsisting of resin, rubber, and ceramic.
 3. A connecting structure fora vacuum pump according to claim 1, further comprising a protectivecover corresponding to the vacuum pump, which is provided around theouter periphery of the connection means.
 4. A connecting structure for avacuum pump according to claim 1, further comprising a damper forabsorbing mechanical vibrations, wherein the electrical insulatingportion is provided to the damper.
 5. A connecting structure for avacuum pump according to claim 4, wherein the damper comprises a bellowsand flanges respectively provided on both ends of the bellows.
 6. Aconnecting structure for a vacuum pump according to claim 5, wherein theelectrical insulating portion is provided so as to surround a part ofthe bellows.
 7. A connecting structure for a vacuum pump according toclaim 5, wherein the flanges are each formed of an electrical insulatingmaterial.
 8. A connecting structure for a vacuum pump according to claim5, wherein one of the flanges has one of an insulating coating and aninsulating plate formed on its end surface, and the flange is fastenedwith an insulating bolt.
 9. A connecting structure for a vacuum pumpaccording to claim 2, further comprising a protective covercorresponding to the vacuum pump, which is provided around the outerperiphery of the connection means.
 10. A connecting structure for avacuum pump according to claim 2, further comprising a damper forabsorbing mechanical vibrations, wherein the electrical insulatingportion is provided to the damper.
 11. A connecting structure for avacuum pump according to claim 10, wherein the damper comprises abellows and flanges respectively provided on both ends of the bellows.12. A connecting structure for a vacuum pump according to claim 11,wherein the electrical insulating portion is provided so as to surrounda part of the bellows.
 13. A connecting structure for a vacuum pumpaccording to claim 11, wherein the flanges are each formed of anelectrical insulating material.
 14. A connecting structure for a vacuumpump according to claim 11, wherein one of the flanges has one of aninsulating coating and an insulating plate formed on its end surface,and the flange is fastened with an insulating bolt.
 15. A connectingstructure for a vacuum pump according to claim 3, further comprising adamper for absorbing mechanical vibrations, wherein the electricalinsulating portion is provided to the damper.
 16. A connecting structurefor a vacuum pump according to claim 15, wherein the damper comprises abellows and flanges respectively provided on both ends of the bellows.17. A connecting structure for a vacuum pump according to claim 16,wherein the protective cover is attached to one of the flanges.
 18. Aconnecting structure for a vacuum pump according to claim 17, whereinthe flanges are each formed of an electrical insulating material.
 19. Aconnecting structure for a vacuum pump according to claim 17, whereinone of the flanges has one of an insulating coating and an insulatingplate formed on its end surface, and the flange is fastened with aninsulating bolt.
 20. A connecting structure for a vacuum pump accordingto claim 1, further comprising a valve for adjusting suction flow rate,wherein the electrical insulating portion is provided to the valve. 21.A connecting structure for a vacuum pump according to claim 20, whereinthe valve has flanges respectively formed on its both ends.
 22. Aconnecting structure for a vacuum pump according to claim 21, whereinthe entirety of the valve is formed of an electrical insulatingmaterial.
 23. A connecting structure for a vacuum pump according toclaim 21, wherein one of the flanges has one of an insulating coatingand an insulating plate formed on its end surface, and the flange isfastened with an insulating bolt.
 24. A connecting structure for avacuum pump according to claim 2, further comprising a valve foradjusting suction flow rate, wherein the electrical insulating portionis provided to the valve.
 25. A connecting structure for a vacuum pumpaccording to claim 3, further comprising a valve for adjusting suctionflow rate, wherein the electrical insulating portion is provided to thevalve.
 26. A connecting structure for a vacuum pump according to claim8, wherein one of the insulating coating and the insulating plate isformed of a buffer material such as rubber.
 27. A connecting structurefor a vacuum pump according to claim 14, wherein one of the insulatingcoating and the insulating plate is formed of a buffer material such asrubber.
 28. A connecting structure for a vacuum pump according to claim19, wherein one of the insulating coating and the insulating plate isformed of a buffer material such as rubber.
 29. A connecting structurefor a vacuum pump according to claim 23, wherein one of the insulatingcoating and the insulating plate is formed of a buffer material such asrubber.
 30. A connecting structure for a vacuum pump according to claim1, wherein the vacuum pump comprises: rotor blades; electromagneticbearing means for magnetically levitating the rotor blades; androtational drive means for rotating the rotor blades.